Boring type of continuous miner having central oscillating cutter drums



March 7, 1967 J. GONSKI BORING TYPE OF CONTINUOUS MINER HAVING 3 sheets sheet 1 Fil edJuly 17, 1964 CENTRALOSCILL-ATING CUTTER DRUMS w my Z N 10A W6 %m m N w 0 I i i BY M March 7, 1967 Filed. July 17, 1964 J. GON I v BORING TYPE OF CONTINUOUS MINER HAVING CENTRAL OSCILLATING CUTTER DRUMS 5 Sheets-Sheet 2 INVENTOR.

Joseph .Go/m/ ATTOP/VEJS T J. GONSKI 3,307,878 BORING TYPE OF CONTINUOUS MINER HAVING CENTRAL OSCILLATING CUTTER DRUMS March 7, 1967 Filed'Jul 17, 1964 3 Sheets-Sheet s- H8 I20 92 H6 30 INVENTOR. Josey/g 60/796 v A7 OI/VEYS United States Patent 3,307,878 BORING TYPE OF CONTINUOUS MINER HAVING CENTRAL OSCILLATING CUT- TER DRUMS Joseph Gonski, Chicago, Ill., assignor, by mesne assignments, to Westinghouse Air Brake Company, Pittsburgh, Pa.

Filed July 17, 1964, Ser. No. 383,473

13 Claims. (Cl. 299--57) This invention rel-ates to improvements in continuous mining machines of the boring type and more particularly relates to an improved form of low height boring type of continuous mining machine having central oscillatably driven cutter drums in the space between the boring heads of the machine. I

A principal object of the present invention is to provide a novel and improved form of low height continuous mining machines of the rotary boring type arranged with a view towards a more adequate throat and conveying capacity, to more efiiciently load the material mined.

Another object of the invention is to provide animprove-d form of low height continuous mining machine of the rotary boring type arranged with a view. towards increasing the capacity of the throat and conveyor of the machine by ripping the coal in the spaces between the boring heads in vertical swaths, generally conforming to the boring diameters of the boring heads.

Afurther object of the invention is to provide a continuous mining machine particularly adapted for mining low or thin seams of coal, in which the reduced cutting diameter of the boring heads made necessary to mine the low seams of coal, is compensated for by widely spacing the boring heads apart on opposite sides of the throat of the conveyor, and by providing oscillating cutter drums in the spaces between the mining heads, for dislodging and breaking down the materialin the spaces between the mining heads and progressing the mined material toward the conveyor of the machine.

A still further object of the invention is to provide a low height continuous mining machine of the rotary boring type having two relatively widely spaced boring heads extending forwardly of the cutter frame of the machine, on opposite sides of the conveyor of the machine, and by mounting rotary cutting and dislodging drums between the boring heads foroscillatable movement about axes coaxial with the axes of rotation of the boring heads, from the floor to the roof of the mine,'to mine in each direction of oscillatable movement thereof, while the drums ro-v tate in one direction.

These and other objects of the invention will appear from time to time as the following specification proceeds and with reference to the accompanying drawings wherein:

FIGURE 1 is a front end view of a continuous mining machine constructed in accordance with the principles of the present invention, with certain parts broken away and certain other parts shown in vertical section;

FIGURE 2 is a fragmentary plan view of the forward end portion of the machine shown in FIGURE 1 with certain parts broken away and certain other parts shown in horizontal section, in order to show the details of the support and drive connection to one of the oscillatibly movable cutter drums;

. FIGURE 3 is a generally diagrammatic end view of a continuous mining machine similar to that shown in FIGURE 1, but showing a different form of cutter drum from that shown in FIGURE 1;

:FIGURE 4 is an enlarged fragmentary plan view of the forward end portion of the machine shown in FIGURE 3, with certain parts broken away and certain other parts 3,307,878 Patented Mar. 7, 1967 ice shown in horizontal section, in order to illustrate the details of one of the cutter drums and the support and drive therefor; and

FIGURE 5 is a fragmentary detail sectional view taken substantially along lines 5--5 of FIGURE 4, and illustrating a form of automatic cycling means for effecting oscillatible movement of the cutter drum.

In the embodiment of the invention illustrated in FIGURES 1 and 2 of the drawings, I have shown the forward end portion of a continuous mining machine 10 of the boring type having a cutter frame 11 supported on a conventional main .frame (not shown), in advance thereof, for adjustable movement about axes extending transversely and longitudinally of said main frame. The machine 10 is supported on the usual continuous traction tread devices (not shown), which serve to tram the machine from working place to working place and to feed a pair of laterally spaced boring heads 12, 12, supported on and extending in advance of the cutter frame 11, into the working face of a mine. The adjustable support for the cutter frame on the main frame may be of any well known form, and is no part of the present invention, so need not herein be shown or described further.

The machine also has a conveyor 13 extending from a position adjacent the ground at the front of the machine and beneath the cutter frame 11 and just rearwardly of a transverse support 15 for a lower trimmer bar 16. The lower trimmer bar 16 extends for substantially the width of the machine, rearwardly of the boring heads 12, 12, and forms a guide means for a continuous trimmer chain 17, guided in said lower trimmer bar to out along the floor of the mine.

The conveyor 13 is shown as being a conventional form of single strand endless chain and flight type of conveyor, and maybe of the laterally flexible type (not shown), to discharge the mined material to either side of the machine, and extends from the ground in advance of the machine along the central portion of the machine beyond the rear end thereof. The trimmer bar support 15 is suspended from the cutter frame 11 on the usual hydraulic jacks (not shown) holding the trimmer bar 16 in position and adjustably moving said trimmer bar with respect to the ground and moving the receiving end portion of the conveyor 13 therewith.

Pusherplates 18, 18 depend from the cutter frame 11 and extend from opposite ri'bs of the working piece along said cutter frame to the conveyor 13 behind the boring heads 12, 12 and lower trimmer bar 16, .toconfine the mined material to be progressed toward the center ofthe machine by said boring heads.

An upper trimmer bar 19 is mounted on the cutter frame 11 in advance of the forward end thereof in vertical alignment with the lower trimmer bar 16, on hydraulic jacks 20. The hydraulic jacks 20 are mounted on the front face of the cutter frame 11 and extend vertically therealong and serve to vertically adjust said trimmer bar with respect to said cutter frame and to hold said trimmer bar in position during the cutting operation.

The trimmer chain 17 is trained along the lower trimmer bar 16 and around corner sprockets 21, 21 at opposite ends of said trimmer bar and angularly inwardly and upwardly therefrom. one run of said trimmer chain is trained around an idler sprocket 22 and angularly outwardly and upwardly therefrom around a corner sprocket 23 at one end of the upper trimmer bar 19. The other run of the trimmer chain is trained angularly inwardly and upwardly around a drive sprocket 24 and angularly outwardly and upwardly therefrom around a corner sprocket 25, at the opposite end of the trimmer bar from a corner sprocket 23. The drive sprocket 24 is suitably driven from gear reduction mechanism journalled in the cutter frame 11 and drives the trimmer chain 17 along the lower and upper trimmer bars 16 and 19 respectively, to out along the floor and roof of the mine between the boring heads 12, 12 and thereby leave an unobstructed floor and roof as the mining operation progresses, to accommodate free feeding movement of the boring heads into the coal seam.

The cutter frame 11 has spaced hubs 27 extending forwardly therefrom from positions disposed adjacent the outer sides thereof. Each hub 27 forms a mounting for thrust bearings 29, forming a bearing mounting for a drive shaft 30 for the boring head. Each drive shaft 30 terminates at its outer end into a dimetral boring arm 31 having a pilot cutter 32 projecting forwardly therefrom, having forwardly projecting cutter bits 33 mounted thereon, for cutting an annular kerf adjacent the center of the seam. The diametral arm 31 has telescopic arms 35 mounted therein for extensible and retractible movement with respect thereto, to vary the cutting diameter of the boring head and to retract the boring head when tramming the machine from working place to working place. The telescopic arms 35 are held in fixed relation with respect to the arm 31 and are extensibly and retractibly moved with respect to said boring arm by a conventional form of adjusting mechanism, which is no part of the present invention, so need not herein be shown or described further. The telescopic arms 35 have cutter supports 36 projecting forwardly therefrom and of an arcuate form in front end View, conforming to the arc of travel of said cutter supports, The cutter supports 36 have the usual cutter bits 37 projecting forwardly therefrom and pitched to cut clearance for said cutter supports to cut annular kerfs in the mine face.

Each cutter support 36 has a plow 38 extending inwardly from the advance end portion thereof toward the center of rotation of the boring head. The plow 38 extends angularly inwardly from the advance end of the cutter support 36 toward the telescopic arm 35, and is pitched to progress the mined material toward the center of the machine, it being understood that the two boring heads 12 rotate in opposite directions to cut from the roof to the floor of the mine and to thereby progress the mined material in front of the conveyor 13.

Each shaft 30 forms the pivotal mounting for an oscillatibly movable arm or boom 39, forming a support for a cutter drum 40 and supporting said cutter drum for rotation about an axis extending radially of the axis of rotation of the shaft 30.

As shown in FIGURE 2, the arm 39 has a hub portion 41 disposed adjacent the boring arm 31 and oscillatibly mounted on the shaft 30 on an anti-friction bearing 42. The hub portion 41 is abutted by a housing 43, extending inwardly of said hub portion and along the arm 39 and forming a housing for a spur gear 45 and a mounting for a bearing 46 mounting the housing on the shaft 30. The housing 43 also houses a reach spur gear train 47, driving a drum drive shaft 48 disposed adjacent the outer end of the arm 39. The spur gear 45 is keyed or otherwise secured to the shaft 30 and driven therefrom and meshes with a driven gear of the reach spur gear train 47 extending along the arm 39, to drive the cutter drum 40 from the shaft 30.

The arm 39 has a bearing support arm 49 extending at right angles with respect thereto in a forward direction and along opposite sides of the shaft 48 and forming a support for annular bearings 50. The annular bearing 50 closest to the adjacent boring head 12, as shown in FIGURE 2, forms a bearing support for a cutter disk 51 having a widened rim 53 journalled on the bearing 50, adjacent its inner end and also forming a support for radially extending cutter supports 54, having cutter bits 55 projecting therefrom. The cutter supports and cutter bits 55 are spaced laterally along the rim 53 to position the cutter bits 55 to cut for the width of said rim and to cut clearance for said rim and the disk 51. The support 4 49 also forms a mounting for an anti-friction bearing 57 for the forward end of the shaft 48.

The housing portion 43 also has a bearing support arm 59 projecting forwardly therefrom, forming a support for annular bearings 60*, on opposite sides thereof. The annular bearing 60, facing the annular bearing 50 on the annular bearing support 49, forms a bearing support for an annular rim 61 of a cutter disk 63. The cutter disk 63 has spaced cutter supports 65 extending radially outwardly of the rim 61 and carrying the usual cutter bits 66.

The cutter disks 63 and 51 are shown as being keyed on a shaft 67 extending through an outer cutter disk 69 and having a conical cutter support 70 welded or otherwise secured to the end thereof. The cutter disk 69 like the cutter disk 51 has a rim 71 journalled in the outer annular bearing 60 and has cutter supports 72 extending radially of the periphery thereof, having cutter bits 73 projecting therefrom. The conical disk 70 is welded or otherwise secured to the end of the shaft 67 and has cutter bit carrying cutter supports 75 projecting from the face thereof,'for cutting and breaking down the material between the two cutter drums 40. The conical cutter support disk 70 forms an end retainer for the cutter drum 40. A nut 76, threaded on the opposite end of the shaft 67 from the conical disk 70, is provided to hold the cutter drum in assembled relation.

The cutter drum is oscillatibly moved back and forth about the axis of the shaft 30' as it is rotatably driven from said shaft by a fluid pressure cylinder 77 having a piston (therein) and a piston rod 79 extensible therefrom. The cylinder 77 is shown in FIGURE 1 as being trunnioned adjacent its head end on trunnion pins 80, 80 pivotally mounted in a trunnion bracket 81, mounted on and extending forwardly of the front face of the cutter frame 11. The piston rod 79 is shown as having a flattened outer end portion 82 extending between the furcations of a bifurcated connector 83 and pivotally connected thereto. The connector 83 extends outwardly of an arm 84 secured to the periphery of the hub 43 and extending rearwardly therefrom. The cylinder 77 is a double acting fluid pressure cylinder to effect angular movement of the arm 39 and cutter drum 40 from the roof to the floor and floor to the roof of the mine by the cyclical admission of fluid under pressure to the head and piston rod ends thereof.

It should here be understood that during the mining operation the two boring heads 12 are rotatably driven as the machine is advanced into a mine face by its continuous traction thread devices (not shown), and the cutter drums 40 are initially positioned to cut along the roof of the mine and are held to cut at roof level and advanced into the mine face a distance sufficient to give the cutter drums a good bite in the coal. The cutter drums are then moved from the roof to floor and floor to roof of the mine while they are rotating in directions to progress the mined material toward the conveyor 13 as the machine is advanced into the face. The cutter drums 40, rotating about axes radially of the axes of rotation of the mining heads 12, thus cut arcuate swaths in the mine face, breaking into the bores cut by said cutter drums and leaving relatively narrow upstanding and de pending cusps between said rotary cutter drums and between said drums and the boring heads, which are cut by .the trimmer chain 17, trimming the floor and roof of the mine in a conventional manner.

In the form of the invention illustrated in FIGURES 3,

4 and 5, I have substituted hollow end cutting cutter dru ms 85 for the cutter drums 40. In this form of the invention the mining heads and the supports therefor are the same as in the form of the invention illustrated in FIGURES 1 and 2, so the end cutting cutter drums, and the supports for said cutter drums need only herein be shown and described in detail, and the same part numbers when referring to the machine proper will be applied to the same parts as in FIGURES 1 and 2.

Each end cutting cutter drum 85 is mounted on the outer end of an individual support arm 86, having a hub 87 journalled on the shaft 30 on an anti-friction bearing 88. A housing 90 extends along the arm 86, and is closed by said arm, and has a hub 91 journalled on the shaft 30 on an anti-friction bearing 92, as in the form of the invention illustrated in FIGURES 1 and 2. The housing 90 and hub 87 form a housing for a sprocket 93, keyed or otherwise secured to the shaft 30. An endless chain 94 meshes with and is driven from the sprocket 93 and drives a sprocket 95 keyed or otherwise secured to a shaft 96, extending parallel to the shaft 30 and outwardly of the arm 86. The shaft 96 is journalled in the arm 86 and housing 90 on anti-friction bearings 97, and 98, respectively. A hub 99 of the end cutting cutter drum 85 is keyed or otherwise secured to the shaft 96 and is retained to said shaft by end cap 100, secured to the end of the shaft 96, as by a machine screw 101. The hub 99 forms a support and drive member for the end cutting cutter drum 85, which extends forwardly therefrom. Cutter bit carrying cutter blocks 103 are mounted on the annular forward end portion of the cutter drum 85 and have cutter bits 105, projecting forwardly therefrom, pitched to cut clearance for said cutter drum.

The end cutting cutter drum 85 also has cutter-bits 106 mounted therein and extending radially of the periphery thereof for performing a cutting operation, as the end cutting cutter drum is sumped into a mine face, and particularly at the top and bottom of the seam.

It should here be understoodthat the end cutting cutter drums 85 are only sumped into the mine face for a short portion of their length, and that the cutter bits 106 adjacent the forward end thereof serve as cutter hits while the cutter bits at the rear end portion of said drum normally serve as gauge bits. Openings 107, 107 are provided in the cylindrical wall of the cutter drum 85 to accommodate the discharge of cuttings from the interior of said drum.

The end cutting cutter drums 85 are oscillatibly moved up and down about the axis of the shaft 30 by operation of double acting hydraulic cylinders 109, in the same manner the cutter drums 40 are oscillatibly moved up and down. Each cylinder 109 is trunnioned on the front face of the cutter frame on trunnion pins 110 and has a piston rod 111 extending from a piston (not shown) movable along said cylinder. The piston rod extends between the furcations of a bifurcated connector 112 and is pivotally connected thereto as by a pivot pin 113. The bifurcated connector 112 extends radially of a bracket arm 115, welded or otherwise secured to the hub 91, and, extending rearwardly therefrom.

As shown in FIGURES 4 and 5 a rotary valve 116 is provided to cyclically supply fluid under pressure to the head and piston rod ends of the cylinders 109. The valve 116 is automatically cycled to effect the oscillatible movement of the end cutting cutter drums 85 from the roof to the floor and floor to roof of the mine during operation of the boring heads 12.

The cycling means for the valve 116 is shown as comprising a lug 117 extending radially of the hub 91 and alternately engaging diverging legs 118 of a generally V-shaped valve operator 119, secured to a rockable valve shaft 120, for operating said valve. The valve 116 is thus pivoted in one direction to admit fluid under pressure to the piston rod ends of the cylinders 109 and release fluid from the head ends of said cylinder when in the position shown in FIGURE 5, and the end cutting outter drums 85 are adjacent the mine roof, and move the valve operator 119 and valve into position to release fluid from the piston rod ends of the cylinders 109, and admit fluid under pressure to the head end of said cylinders, to effect upward movement of the end cutting cutter drums 85, as said cutter drums approach the mine floor. The two end cutting cutter drums mayv thus be oscillatibly cycled from the room to the floor and floor to the that at this time the forwardmost bits 106 effect a cutting operation along the roof in cooperation with the bits 105, while the rearwardmost bits 106 effect a gauging operation. The cutter drums are also driven at sufficiently high rates of speed that their cutter bits will effect a cutting operation during down and up movement of said cutter drums, and the two cutter drums are both rotated to progress the cuttings toward the center of the machine.

While I have herein shown and described one form in which the invention may be embodied, it may readily be understood that various variations and modifications in the invention may be obtained without departing from the spirit and scope of the novel concepts thereof.

I claim as my invention:

1. In a continuous mining machine a cutter frame supported in vertically spaced relation with respect to the ground and for movement toward a working face of a mine,

a pair of widely spaced boring heads mounted on said cutter frame and extending in advance thereof and having cutter supports projecting forwardly therefrom,

a pair of oscillatibly movable cutter drums disposed inwardly of said boring heads and means mounting said cutter drums on said cutter frame for oscillatible movement in the space between said cutter drums from the roof to the floor of a mine about laterally spaced axes extending longitudinally of the machine.

2. A continuous mining machine in accordance with claim 1 wherein the oscillatibly movable cutter drums are supported for oscillatible movement about axes coaxial with the axes of rotation of said boring heads and wherein power means are provided for oscillatibly moving said cutter drums from the floor to the roof .and roof to fioor of a mine.

3. In a continuous mining machine,

a cutter frame supported in vertically spaced relation with respect to the ground and for movement toward the working face of a mine,

a pair of widely spaced boring heads mounted on said cutter frame adjacent opposite sides thereof,

said boring heads being rotatably driven about axes extending longitudinally of the machine and having cutter supports projecting forwardly therefrom having cutter bits projecting therefrom and rotatably driven to cut from the roof to floor of a mine in a direction toward. the center of the machine,

a pair of oscillatibly movable arms mounted for movement about axes coaxial with the axes of rotation of said boring heads and extending inwardly therefrom,

an individual cutter drum rotatably supported on each arm in radial spaced relation with respect to the axes of oscillatible movement of said arms,

means retaining said arms in position and oscillatibly moving said arms to feed said cutter drums up and down from one extremity to the other of the working face of the mine,

and drive means for rotatably driving said cutter drums to mine the material between said boring heads upon up and down feeding movement of said arms.

4. In a continuous mining machine,

a cutter frame supported in vertically spaced relation with respect to the ground and for feeding movement toward the working face of a mine,

two widely spaced rotary boring heads mounted on said cutter frame adjacent opposite ends thereof and extending in advance thereof and having cutter supports projecting forwardly therefrom,

rotatably driven support and drive shafts for said boring heads journalled in said cutter frame,

a rotary cutter drum in association with each boring head,

said cutter drurns being oscillatibly movable in the space between said boring heads,

support means for said cutter drums comprising arms pivotally mounted on said boring head drive shafts and extending inwardly therefrom,

rotatable support means for said cutter drums rotatably supporting said cutter drums adjacent the free ends of said arms and forwardly thereof,

means oscillatibly moving said arms about the axes of said boring head drive shafts,

and drive means for rotatably driving said cutter drums.

5. A continuous mining machine in accordance with claim 4 wherein said rotatable cutter drums are end about axes extending radially of the axes of rotation of said boring head drive shafts.

6. A continuous mining machine in accordance with claim 4 wherein said rotatably cutter drums are end cutting cutter drums and are supported and driven about axes extending parallel to the axes of rotation of said boring head drive shafts.

7. A continuous mining machine comprising:

a mobile main frame,

a cutter frame mounted on said main frame and extending in advance thereof,

a conveyor beneath said cutter frame and extending from a position adjacent the ground in advance of said main frame rearwardly along said main frame beyond the rear end thereof,

upper and lower trimmer cutting means mounted on said cutter frame and being effective to out along the floor and roof of a mine,

two widely spaced rotary boring heads mounted on said cutter frame in advance of said upper and lower trimmer cutting means for rotation about axes extending longitudinally of said main frame and having cutter 'bit carrying cutter supports projecting forwardly therefrom and driven about axes extending longitudinally of the machine in directions to progress the cuttings toward the center of the machine in advance of said conveyor,

two oscillatibly movable rotary cutter drums in the space between said boring heads, support arms for said rotary cutter drums mounted on said cutter frame for oscillatible movement about axes coaxial with the axes of rotation of said boring heads and drive means for rotatably driving said cutter drums.

8. A continuous mining machine in accordance with claim 7 in which the cutter drums rotate about axes extending radially of the axes of rotation of said boring heads and are rotatably driven to progress the cuttings rearwardly toward said conveyor.

9. A continuous mining machine in accordance with claim 7 in which the cutter drums are supported for rotation about axes extending parallel to the axes of rotation of said boring heads and have end cutter bits projecting forwardly therefrom and other cutter bits projecting radially of the peripheries thereof.

10. A continuous mining machine in accordance with claim 9 wherein hydraulic cylinder and piston means are provided for oscillatibly moving said arms and cutter drums, wherein a four way valve is provided to control the admission and release of fluid under pressure to said hydraulic cylinder and piston means, and wherein an operative connection is provided between one of said support arms and the valve associated therewith to shift said valve at the end of each up and down stroke of said cutter drums to effect automatic cycling of said cutter drums during rotatable movement of said boring arms.

11. In a continuous mining machine:

a main frame,

a cutter frame mounted on said main frame,

two laterally spaced rotary boring heads mounted on said cutter frame in widely spaced relation with respect to each other and having rotatably driven longitudinally extending drive shafts extending forwardly of said cutter frame,

radial boring arms mounted on the ends of said shafts and having cutter bit carrying cutter supports projecting forwardly therefrom,

upper and lower trimmer cutter means mounted behind said boring heads and being effective to cut along the floor and roof of a mine between said boring heads,

a support arm journalled on one of said longitudinally extending drive shafts and extending radially inwardly therefrom,

a cutter drum having cutter bits projecting from the periphery thereof rotatably supported on said support a-r-m adjacent the free end thereof and extending forwardly of said arm between said boring heads,

drive means driven from said longitudinally extending drive shaft and extending along said support arm for driving said cutter drum, and

hydraulic cylinder and piston means for oscillatibly moving said support arm to feed said cutter drum from the roof to th floor and floor to roof of a mine.

12. A continuous mining machine in accordance with claim 11 wherein the cutter drum is journalled for rotation about an axis extending radially of the axis of rotation of said boring head support and drive shaft.

13. A continuous mining machine in accordance with claim 11 wherein the cutter drum is rotatable about an axis parallel to the axis of rotation of said boring head support and drive shaft and has cutter bits projecting from the end thereof.

References Cited by the Examiner UNITED STATES PATENTS 2,595,398 5/1952 Lewis 29986 X 2,823,023 2/1958 Hlinsky 29959 X 3,096,082 7/1963 Long- 29959 X ERNEST R. PURSER, Primary Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 307 ,878 March 7 1967 Joseph Gonski d that error appears in the above numbered pat It is hereby eertifie d Letters Patent should read as ent requiring correction and that the sai corrected below.

Column 2, line 46, for "piece" read place column 4 line 49, for "thread" read tread column 5, line 75, for "room" read roof column 7 line 18 strike out d" and insert instead "said rotatable cutter drums are en the cutter drums are rotatable driven Signed and sealed this 21st day of November 1967 (SEAL) Attest:

EDWARD J BRENNER Edward M. Fletcher, Jr.

Commissioner of Patents Attesting Officer 

1. IN A CONTINUOUS MINING MACHINE A CUTTER FRAME SUPPORTED IN VERTICALLY SPACED RELATION WITH RESPECT TO THE GROUND AND FOR MOVEMENT TOWARD A WORKING FACE OF A MINE, A PAIR OF WIDELY SPACED BORING HEADS MOUNTED ON SAID CUTTER FRAME AND EXTENDING IN ADVANCE THEREOF AND HAVING CUTTER SUPPORTS PROJECTING FORWARDLY THEREFROM, A PAIR OF OSCILLATIBLY MOVABLE CUTTER DRUMS DISPOSED INWARDLY OF SAID BORING HEADS AND MEANS MOUNTING SAID CUTTER DRUMS ON SAID CUTTER FRAME FOR OSCILLATIBLE MOVEMENT IN THE SPACE BETWEEN SAID CUTTER DRUMS FROM THE ROOF TO THE FLOOR OF A MINE ABOUT LATERALLY SPACED AXES EXTENDING LONGITUDINALLY OF THE MACHINE. 